The Contractor shall provide computer-related technical support services, primarily systems design, computer programming, system documentation and operational support to the Biometry Research Group, Division of Cancer Prevention, in the National Cancer Institute, the National Institutes of Health. The computer-related support falls into three main categories: data management, systems design and development and statistical analysis and modeling. One of the projects for which the Contractor will provide support is the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, or PLCO, which is a large-scale clinical trial to determine whether certain cancer screening tests reduce deaths from these cancers. The underlying rationale for the trial is that screening for cancer may enable discovery and treatment of the disease earlier. The cancer prevention aspect is related to the design that tests whether the introduction of screening reduces mortality. The screening studies for these four cancers can be considered as four separate projects for description purposes. The screening studies for prostate cancer have as the objective to evaluate the ability of prostate cancer screening tests to reduce deaths from one of the four cancers in the PLCO study. There are 75,000 men participating in the PLCO study who are at normal risk for developing prostate cancer. Participants are randomly assigned to one of two groups, the intervention group or the control group. The intervention group receives: PSA (men only), at initial visit and annually for 5 years (screening for prostate cancer) Digital rectal exam (men only), at initial visit and annually for 3 years (screening for prostate cancer) Flexible sigmoidoscopy, at initial visit and after 5 years in study Chest X-ray: smokers had test at entry and annually for 3 years. Never smokers had the test at entry and annually for 2 years. The control group receives usual care. Note that these are randomized controlled trials where the endpoints are designed to test whether the introduction of screening reduces mortality from the particular cancer in question.